Survival outcome and prognostic factors of remnant gastric cancer: a propensity score-matched analysis

Background: Studies on survival and prognostic factors in individuals with remnant gastric cancer (RGC) after gastric cancer (GC) are rare. It is debatable whether prognosis of RGC after GC is worse than that of only primary GC (OPGC). The objective of this study is to compare the survival outcomes between post- GC RGC and OPGC undergoing surgical resection and to identify the prognostic factors of disease-specific survival (DSS) for RGC. Methods: We retrospectively collected data from the Surveillance, Epidemiology, and End Results (SEER) database among patients who underwent GC surgery in 1988-2020. Propensity score matching (PSM) was conducted to balance baseline characteristics. Kaplan-Meier (KM) survival analysis was performed to compare their overall survival (OS) and DSS. Multivariable Cox analyses were performed to identify the independent prognostic factors of DSS for post-GC RGC by estimating hazard ratios (HRs) with 95% confidence intervals (CIs). Results: There were 76 patients with RGC and 32,763 patients with OPGC included and analyzed. After balancing the baseline characteristics by PSM, no significant difference existed between OPGC and RGC groups in both OS (P=0.65) and DSS (P=0.28). Fixed-time analyses also showed no difference between the two groups for the 5-year (60.0%, RGC vs . 53.3%, OPGC, P=0.38) and 10-year DSS (56.7%, RGC vs . 48.3%, OPGC, P=0.34). Multivariable analysis revealed that area of lower income ($75,000+ vs . <$55,000, HR =0.21, 95% CI: 0.05-0.89, P=0.03), cardiac tumor [middle vs . cardia, HR =0.16, 95% CI: 0.03-0.77, P=0.02; distal vs . cardia, HR =0.10, 95% CI: 0.02-0.58, P=0.01; not otherwise specified (NOS) vs . cardia, HR =0.11, 95% CI: 0.03-0.51, P=0.004], deeper invasion (T3-4 vs . Tis-2, HR =5.19, 95% CI: 1.21-22.15, P=0.03), higher grade (G3 vs . G1-2, HR =7.35, 95% CI: 1.41-38.48, P=0.02) and not receiving chemotherapy (yes vs . no/unknown, HR =0.16, 95% CI: 0.04-0.60, P=0.007) were independent risk factors for postsurgical DSS in patients with post-GC RGC. Conclusions: The prognosis of post-GC RGC was comparable to that of OPGC following surgical resection. The independent prognostic factors for RGC are similar to those established for OPGC. Our findings suggest that RGC following first GC might be the same entity to OPGC and curative resection should be considered in selected patients.